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Geothermal Heat Pumps, Using the Earth to Save Energy

Geothermal heat pumps (GHPs), sometimes referred to as GeoExchange, earth-coupled, ground-source, or water-source heat pumps, have been in use since the late 1940s. They use the relatively constant temperature of the earth as the exchange medium instead of the outside air temperature.

The geothermal heat pump, also known as the ground source heat pump, is a highly efficient renewable energy technology that is gaining wide acceptance for both residential and commercial buildings. Geothermal heat pumps are used for space heating and cooling, as well as water heating. The benefit of ground source heat pumps is they concentrate naturally existing heat, rather than producing heat through the combustion of fossil fuels.

Although many parts of the country experience seasonal temperature extremes -- from scorching heat in the summer to sub-zero cold in the winter—a few feet below the earth's surface the ground remains at a relatively constant temperature. Depending on latitude, ground temperatures range from 45°F (7°C) to 75°F (21°C).

Like a cave, this ground temperature is warmer than the air above it during the winter and cooler than the air in the summer. The GHP takes advantage of these more favorable temperatures to become highly efficient by exchanging heat with the earth through a ground heat exchanger.

As with any heat pump, geothermal and water-source heat pumps can heat, cool, and, if so equipped, supply the house with hot water. Some models of geothermal systems are available with two-speed compressors and variable fans for more comfort and energy savings. Relative to air-source heat pumps, they are quieter, last longer, need little maintenance, and do not depend on the temperature of the outside air.

What is geothermal energy? Geothermal energy is heat within the earth. The word geothermal comes from the Greek words geo (earth) and therme (heat). Geothermal energy is a renewable energy source because heat is continuously produced inside the earth. People use geothermal heat for bathing, to heat buildings, and generating electricity.

Geothermal energy comes from deep inside the earth The slow decay of radioactive particles in the earth's core, a process that happens in all rocks, produces geothermal energy.

The earth has four major parts or layers:

  1. An inner core of solid iron that is about 1,500 miles in diameter

  2. An outer core of hot molten rock called magma that is about 1,500 miles thick

  3. A mantle of magma and rock surrounding the outer core that is about 1,800 miles thick

  4. A crust of solid rock that forms the continents and ocean floors that is 15 to 35 miles thick under the continents and 3 to 5 miles thick under the oceans

Scientists have discovered that the temperature of the earth's inner core is about 10,800 degrees Fahrenheit (°F), which is as hot as the surface of the sun. Temperatures in the mantle range from about 392°F at the upper boundary with the earth's crust to approximately 7,230°F at the mantle-core boundary.

The earth's crust is broken into pieces called tectonic plates. Magma comes close to the earth's surface near the edges of these plates, which is where many volcanoes occur. The lava that erupts from volcanoes is partly magma. Rocks and water absorb heat from magma deep underground. The rocks and water found deeper underground have the highest temperatures.

Some applications of geothermal energy use the earth's temperatures near the surface, while others require drilling miles into the earth. There are three main types of geothermal energy systems:

  1. Direct use and district heating systems

  2. Geothermal power plants

  3. Geothermal heat pumps

Direct use and district heating systems Direct use and district heating systems use hot water from springs or reservoirs near the earth's surface. Ancient Roman, Chinese, and Native American cultures used hot mineral springs for bathing, cooking, and heating. Today, many hot springs are still used for bathing, and many people believe the hot, mineral-rich waters have health benefits.

Geothermal energy is also used to directly heat individual buildings and to heat multiple buildings with district heating systems. Hot water near the earth's surface is piped into buildings for heat. A district heating system provides heat for most of the buildings in Reykjavik, Iceland.

Industrial applications of geothermal energy include food dehydration (drying), gold mining, and milk pasteurizing.

Geothermal electricity generation Geothermal electricity generation requires water or steam at high temperatures (300° to 700°F). Geothermal power plants are generally built where geothermal reservoirs are located, within a mile or two of the earth's surface. The United States leads the world in the amount of geothermal electricity generation. In 2021, there were geothermal power plants in seven states, which produced about 16 billion kilowatt-hours (kWh) (or 16,238,000 megawatt-hours), equal to about 0.4% of total U.S. utility-scale electricity generation. Utility-scale power plants have at least 1,000 kilowatts (or 1 megawatt) of electricity generation capacity, equal to 0.4% of total U.S. utility-scale electricity generation.

International geothermal electricity generation In 2019, 27 countries, including the United States, generated a total of about 88 billion kWh of electricity from geothermal energy. Indonesia was the second-largest geothermal electricity producer after the United States, at nearly 14 billion kWh of electricity, which was equal to about 5% of Indonesia’s total electricity generation. Kenya was the eighth-largest geothermal electricity producer at about 5 billion kWh, but it had the largest percentage share of its total annual electricity generation from geothermal energy at about 46%.

Geothermal heat pumps Geothermal heat pumps use the constant temperatures near the surface of the earth to heat and cool buildings. Geothermal heat pumps transfer heat from the ground (or water) into buildings during the winter and reverses the process in the summer. Watch the following video to see how it works. Energy 101: Geothermal Heat Pumps

Geothermal Heat Pumps Benefits for Homeowners and Businesses

Geothermal Heat Pumps are Quiet Buried deep underground, geothermal systems are virtually silent. In contrast to traditional outdoor HVAC condensing units, which can crank on and off and noisily hum all day long.

Energy Savings Geothermal heating units do not use any fossil fuels, they deliver exceptional efficiency. According to Energy Informative, homeowners can save up to 30-70 % on electric heating costs using geothermal heat pumps instead of conventional HVAC systems. Depending on your home's size and energy habits/demands, a geothermal heating system can save you anywhere from $400 to $1,500 annually.

Local Rebates and Tax Credits To incentivize homeowners to convert their HVAC systems to geothermal sources, the federal government created a 26% federal geothermal tax credit (with no cutoff limit) in December 2020. Hoping to reduce carbon emissions, congress extended this year-end bill to cover all residential ground source heat pumps (GSHP) installed before 12/31/2022. Many local utility companies also offer tax credits to offset costs.

If you are looking for an HVAC Contractor to install a geothermal heating system, give Cochran Complete Services a call today! Our specialists are ready and waiting to assist you – every step of the way.

We will visit your home, assess your landscape and property, discuss your energy needs, and learn your price range. Finally, if you decide to invest in a geothermal heating system, we’ll be there to make sure your system is meticulously installed and receives continual care and service.


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